Another great solution is rubber mats. It won't keep a piece totally immobilized, but that isn't always necessary. It works perfectly when you're using a random orbit sander, and you only need to keep the workpiece from sliding around. Clamps can get in the way of the sander. Rubber mats are inexpensive and can be purchased at any department store. The rubber is a bit tacky and creates enough friction to hold a workpiece. They also work well for routing. The mat can hold large panels in place while routing a profile edge. When dust reduces the grip of the mat washing it with warm, soapy water will bring it back to a good tacky condition. These are just a couple easy and cheap solutions.